Identify and Treat Eight Summer Skin Rashes

What it looks like: Tiny fluid-filled blisters in a linear or crisscross pattern.

How you get it: Direct contact with poison ivy, poison oak, or poison sumac. All three plants contain the toxin urushiol, which most people are allergic to. If you’ve been exposed before, you’ll likely notice the rash within 48 hours, but blisters can take up to ten days to appear if it’s your first encounter, says Nelson.

Treat it: For mild cases, OTC calamine lotion should control itching. In more severe cases, use an antihistamine. Go for a topical cream if the rash is contained, and for more spread-out rashes use an oral diphenhydramine, like Benadryl Allergy tablets ($8, drugstore.com), non-drowsy Zyrtec ($27, drugstore.com) or Claritin ($20, cvs.com). Still scratching? Hydrocortisone cream packs the strongest punch by reducing the inflammation that’s causing the itch.

See a doc if: The OTC lineup doesn’t kick the itch within a week (the irritation should subside in about three to five days), or if the rash lingers past a couple of weeks.

Your best defense: First off, follow the old adage, “Leaves of three, let it be.” If you suspect you’ve been exposed, wash the area with soap and water within 15 minutes of contact—you may be able to avoid catching a rash. And beware: Clothing, garden tools, or even pets that have been exposed to poison ivy, oak or sumac, can spread the toxin.

Ragweed

What it looks like: Small, itchy bumps and blisters, and hives in severe cases. Your rash will likely be accompanied by a runny nose, itchy throat, and dry, scratchy eyes.

How you get it: A ragweed-triggered rash is an allergic reaction to the pollen in the plant.

See a doc if: Symptoms persist even after on an OTC regimen, or if you develop a fever, shortness of breath, or abdominal pain.

Your best defense: The less pollen you’re exposed to, the better—easier said than done when you’re outdoors during the summer months. If you’re overly sensitive, ask your doctor about cromolyn, a nasal spray that may thwart your over-the-top reaction.